The 29-year-old back row forward has had three injury-hit seasons with the Rodney Parade region since signing from Pontypridd in 2009.

With the Dragons well-stocked for opensides – with Lewis Evans and Nic Cudd backed up by Wales Under-20s prospects James Benjamin, Scott Matthews and Ollie Griffiths – they have allowed him to join the Exiles.

London Welsh head coach Justin Burnell said: “I’ve known Darren for a long time, going back to watching him during his time at Pontypridd and then at the Dragons, and he’s a sheer raw talent.

“He’s phenomenal at the breakdown, one of the best I’ve seen, and he has an abundance of energy. He’s going to be an absolutely fantastic asset and a really positive addition to our environment.”

Waters earned a professional deal after catching the eye with his abrasive performances in the Principality Premiership.

He did well in his first season, making 13 appearances in 2011/12, but suffered knee ligament damage in a pre-season friendly against London Irish in 2012 before enduring a repeat the following summer.